package org.emergent.android.weave.client;

import java.io.IOException;
import java.io.OutputStream;

class HexEncoder {

	protected final byte[] encodingTable = { (byte) '0', (byte) '1',
			(byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6',
			(byte) '7', (byte) '8', (byte) '9', (byte) 'a', (byte) 'b',
			(byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f' };

	/*
	 * set up the decoding table.
	 */
	protected final byte[] decodingTable = new byte[128];

	public HexEncoder() {
		initialiseDecodingTable();
	}

	/**
	 * decode the Hex encoded byte data writing it to the given output stream,
	 * whitespace characters will be ignored.
	 * 
	 * @return the number of bytes produced.
	 */
	public int decode(byte[] data, int off, int length, OutputStream out)
			throws IOException {
		byte b1, b2;
		int outLen = 0;

		int end = off + length;

		while (end > off) {
			if (!ignore((char) data[end - 1])) {
				break;
			}

			end--;
		}

		int i = off;
		while (i < end) {
			while (i < end && ignore((char) data[i])) {
				i++;
			}

			b1 = decodingTable[data[i++]];

			while (i < end && ignore((char) data[i])) {
				i++;
			}

			b2 = decodingTable[data[i++]];

			out.write((b1 << 4) | b2);

			outLen++;
		}

		return outLen;
	}

	/**
	 * decode the Hex encoded String data writing it to the given output stream,
	 * whitespace characters will be ignored.
	 * 
	 * @return the number of bytes produced.
	 */
	public int decode(String data, OutputStream out) throws IOException {
		byte b1, b2;
		int length = 0;

		int end = data.length();

		while (end > 0) {
			if (!ignore(data.charAt(end - 1))) {
				break;
			}

			end--;
		}

		int i = 0;
		while (i < end) {
			while (i < end && ignore(data.charAt(i))) {
				i++;
			}

			b1 = decodingTable[data.charAt(i++)];

			while (i < end && ignore(data.charAt(i))) {
				i++;
			}

			b2 = decodingTable[data.charAt(i++)];

			out.write((b1 << 4) | b2);

			length++;
		}

		return length;
	}

	/**
	 * encode the input data producing a Hex output stream.
	 * 
	 * @return the number of bytes produced.
	 */
	public int encode(byte[] data, int off, int length, OutputStream out)
			throws IOException {
		for (int i = off; i < (off + length); i++) {
			int v = data[i] & 0xff;

			out.write(encodingTable[(v >>> 4)]);
			out.write(encodingTable[v & 0xf]);
		}

		return length * 2;
	}

	private boolean ignore(char c) {
		return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
	}

	protected void initialiseDecodingTable() {
		for (int i = 0; i < encodingTable.length; i++) {
			decodingTable[encodingTable[i]] = (byte) i;
		}

		decodingTable['A'] = decodingTable['a'];
		decodingTable['B'] = decodingTable['b'];
		decodingTable['C'] = decodingTable['c'];
		decodingTable['D'] = decodingTable['d'];
		decodingTable['E'] = decodingTable['e'];
		decodingTable['F'] = decodingTable['f'];
	}
}
